Electrical control circuit



Oct. 10, 1939. BLUME 2,175,870 I ELECTRICAL CONTROL CIRCUIT Filed July17, 1956 Inventor; Louis F. Blume,

. a adw by His Attorng.

Patented on. 10, 1939 PATENT OFFICE swc'mrcar. ooN'rnor. cmcm'r Louis I.Blume, Pittsiield, Mala, a-ignor to General Electric York , acorporation of New Application July 17, 1838, Serial No. SL130 6 Claims.(CL 171-119) My invention relates toelectrical c ntrol circuits and moreparticularly to voltag responsive control circuits for automatic voltageregulators.

Contact making voltmeters, which are usually used to control inductionvoltage regulators and transformer tap changing devices, must be desgned to control the driving motor within a relatively narrow voltageband width., This band width insome instances is less than 1% of thenormal voltage on which the contact making voltmeter operates. Thisrequirement make s the contact making voltmeter a precise instrumentwith delicately mounted contact. It is therefore not so sturdy a deviceas is desired for this type of service and it is relatively expensive.

In order to eliminate these disadvantages of the contact makingvoltmeter I use two primary contact making relays, one of whichfunctions only to control the motor when the voltage exceeds adeiinitevalue and the other ,functions only to.

control the motor when the voltage is less than a definite value. Itbecomes possible by this separation of functions to make use of a simplevoltage relay which, when the critical upper voltage is reached willmake firm contact so that a considerable motor current, for instance 5or 10 amperes, can be very easily taken care of. A re ay so designed,however, when contact is once made, will not oi its own accord breakcontact when the voltage again becomes normal. In other words. such arelay operates on extremely wide band width. For example, it may bedesigned to be actively sensitive to close contacts at precisely 110volts but will not open contacts until the voltage across the operatingwinding is reduced to as low as 30 volts. To overcome this difiiculty Iprovkie a resetting means for the relay under the control of theregulating means whose operation is in turn controlled by the relay.

While my invention is described in detail in connection with automaticvoltage regulation it should be understood that it is not so limited inapplication and that it can be used in almost any automatic electricalregulating or control system of any variable quantity.

An object of my inventionis to provide a new and improved controlcircuit.

Another object of my invention is to provide a voltage control circuitfor automatic regulators utilizing ordinary relatively inexpensive andinsensitive relays or contactors.

My invention will be better understood from the following descriptiontaken in connection with the accompanying drawing and its scope will bepointed out in the appended claims.

Referrlngnow to the single figure of the accompanying drawing, I haveillustrated diagrammatically therein a typical tap changing auto-'transformer or step voltage regulator consisting of a primary windingland a secondary winding causing it to p 2 provided with taps which areelectrically connected to a tap changing switch 3. These windings areconnected so that voltage may be main tained substantially constantacross a distribution circuit l by the appropriate selection of taps bythe tap changing switch 3. This tap changing switch 3 is operated by amotor 5 through a gear train G in the ordinary manner.

Motor 5 is illustrated by way of example as a capacitor motor and intypical transformer step voltage regulators it has about a 1/100 H. P.rating. One terminal of the motor is directly connected to the lowerconductor of the circuit 4 and when terminal 1 of the motor is connectedto the upper conductor of the circuit 4 the motor operates in adirection to cause the regulating transformer to lower the voltage ofthe circuit and when terminal 8 of the motor is connected to the upperconductor of the circuit 4 the motor 5 will reverse its direction andthe regulating transformer raises the voltage of the circuit l. Voltageis applied to the terminal 1 by means of an overvoltage or lower relay 8which is designed so as to close its contacts at a critical voltage, forexampie volts, and voltage is applied to the terminal 8 by anunder-voltage or raise relay in when the voltage or the circuit 4 fallsto a critical voltage such for example as 198 volts.

Arranged to go through a make and break cycle for each tap changingoperation of the regulator are four sets of contacts H, 52, i3 and H.These contacts are shown by way of example as commutator type contactsmounted on an appropriate shaft I! of the tap changing mechanism, whichshaft makes one complete revolution for each tap changing operation.Contacts I l and ii are for the purpose of resetting the over-voltagerelay 9 and the under-voltage relay Ill, respectively, while contacts.12 and H are sealing in contacts for continuing operation of theregulator until a tap change has been completed after the overvoltageand under voltage relays have been reset.

A resistor i8 cooperateswith the contacts I! for resetting the relay itas will now be described.

The operation of the illustrated embodiment of my invention is asfollows: As the contacts of the under-voltage or raise relay ID areshown closed the voltage of the circuit 4 is below the critical voltage(108 volts for example) at which this relay is set to drop out. Theclosed contacts 01' the relay ll complete a circuit for energizing themotor I and cause it to turn in such a direction as to raise thevoltage-of the circuit. As the motor turns, the shaft II is driventhereby and after the shaft has rotated through a small angle contactsit, which are normally open, close and short circuit resistance Itthereby relatively greatly increasing the energixation of the relay l0and At the same time, commutameans for varying said quantity,

tor contacts ll close thereby completing a seal-in circuit around thecontacts of the relay in. Consequently, although relay I0 is reset bythe contacts IS the contacts ll continue the energization of the motor5. When a tap change has been completed the commutator contacts willagain be in the position shown in the drawing. If the voltage is above108 volts relay ID will remain open and the motor will come to rest.However, if the voltage of circuit 4 is still below 108 volts relay inwill again drop out and cause the regulator to go through another tapchanging operation thereby raising the voltage another step. This willcontinue until the voltage is above the critical voltage at which therelay l0 drops out.

If now the voltage should rise above the critical value at whichover-voltage or lower relay 9 operates it will close its contactsthereby energizing the motor 5 for .reverse operation whereby the tapchanging device will operate in a direction to lower the voltage-oicircuit 4. After a predetermined angular motion of the shaft IS thecommutator contact device II will break the circuit through the relay 9thereby resetting this relay by causing it to drop out. Simultaneouslywith this operation of the contacts I l the commutator contact 12 willcomplete a bridging or seal-in circuit around the contacts of relay 9 sothat the motor 5 continues to be energized until a complete tap changingoperation has been made. If the voltage is still above volts the relay 9will close again and the system wi l go through another voltage loweringtap change. This will continue until the voltage is below 110 volts.

With the above described arrangement it is possible to use very simple,inexpensive relays and to design them to handle the control currentwithout chatter and to make ciently heavy to insure an extremely longlife.

While I have shown and described a particular embodiment of myinvention, it will be obvious to those skilled in the art that changesand modifications can be made, and I aim, therefore, in the appendedclaims to v cover all such changes and modifications as come within thetrue spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

i. In an automatic electrical control system, apparatus having avariable electrical quantity the magnitude of which in at least onedirection is to be limited to a particular value, adjustable anelectro-responsive device connected to be energized in proportion to themagnitude of said quantity, said device being arranged to cause saidadjustable means to reverse the direction of change of said quantityafter said quantity reaches its limited value, and means under thecontrol of said ad- Justable means for positively resetting saidelectro-responsive device after it causes operation of said adJustablemeans and independently of the magnitude of said electrical quantity.

2. In an automatic step regulating system, primary raise and lowerrelays each of which is energized in proportion to the value of theregulated quantity, regulator driving means whose starting and directionof operation is controlled by said relays, and auxiliary meanscontrolled by said driving means for sealing said driving means in for aregulating step and positively resetting said the contacts sum- 7 relaysindependently of the value of the regulated quantity after they startsaid driving means and before a regulating step is completed.

3. In an automatic variable-ratio-transformer type voltage regulatingsystem, ing means, primary voltage responsive raise and lower relays forstarting said operating means, and auxiliary contacts controlled by saidoperating means for respectively positively resetting each relayindependently of the regulated voltage and establishing a seal inconnection for each relay.

4. In a voltage regulating system for a circuit whose voltage tends tovary, a raise relay connected to close a set of contacts when thevoltage of said circuit falls below a predetermined value,

a lower relay connected to close a set of contacts.

when the voltage or said circuit rises above a predetermined value, aregulator driving motor whose direction of operation is controlled bythe respective closure of said contacts, two sets of auxiliary contactsoperated by said motor when it is started by said raise relay forrespectively resetting said raise relay by increasing its energizationand continuing the operation of said motor long enough to provide aregulating effect, and two additional sets of contacts operated by saidmotor when it is started by said lower relay for respectively resettingsaid lower relay by decreasing its energization and continuing theoperation of said motor long enough to produce a regulative effect.

5. In a regulating system comprising a reversible electric motor, araise relay having an operating winding and a set of contacts forcontrolling a circuit of said motor to operate it in one direction, alower relay having an' operating winding and a set oi contacts forcontrolling a circuit of said motor to operate it in the reversedirection, and a plurality of switches coupled to be operated by saidmotor, one pair of said switches being arranged for controlling saidraise relay so that a circuit around its contacts and a circuit inseries relation with its operating winding are 'open concurrently andclosed concurrently, the other pair of said switches being arranged forcontrolling said lower relay so that a circuit around its contacts and acircuit in series relation with its operating winding are opennon-concurrently and closed non-concurrently.

6. In combination, apparatus having a variable quantity to be regulated,a pair of primary relays in the form of conventional contactorsconnected to be energized in proportion to the value of said quantity,said relays having a relatively wide range of energization between theirpull-in and drop-out values, a movable regulator arranged to becontrolled by one of said relays to raise the value of said quantity itit falls below a predetermined value andarranged to be controlled by theother of said relays to lower the value of said quantity it it risesabove a predetermined value, and means for permitting said predeterminedvalues to be so close to each other that the normal unmodified pull-into drop-out ranges oi energization of said relays overlap comprisingauxiliary means for positively resetting whichever of said relays hascaused operation of said regulator.

LOUIS F. BLUME.

regulator operat-

